130 lines
4.3 KiB
NASM
130 lines
4.3 KiB
NASM
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; Goes through drives A-Z and determines if they:
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; 1) Exist
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; 2) Are removable or fixed
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; 3) Are local, remote, or shared
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; 4) Are a floppy, hard, RAM, subst, or CD-ROM drive
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;
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; Callable from C as: void Drives_Exist(void);
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.model small
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.286
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DRIVEEXIST EQU 1
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REMOVEDRV EQU 0
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FIXEDDRV EQU 1
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LOCALDRV EQU 0
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REMOTEDRV EQU 1
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SHAREDRV EQU 2
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FLOPPY EQU 0
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HARD EQU 1
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RAM EQU 2
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SUBST EQU 3
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CDROM EQU 4
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.data
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PUBLIC _drives
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_drives db 26 dup(0,1,0,1)
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; default to not exist, fixed, local, hard drive
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.code
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PUBLIC _Drives_Exist
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_Drives_Exist PROC NEAR
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pusha
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push es
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mov ah,19h
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int 21h ; get start drive
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push ax ; save start drive
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mov ax,40h
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mov es,ax
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mov bh,es:[10h] ; 40:10h is # of floppies-1
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shr bh,6
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inc bh ; # of actual floppy drives
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mov bl,1
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mov di,offset _drives
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nextchkfloppy: mov ax,4409h ; check if drive exists
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int 21h
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jc nextsetfloppy
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test dh,10000000b ; check if SUBST drive
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jz chkfloppy
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dec bh ; dec actual drive count
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mov byte ptr [di+3],SUBST
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setfloppyexist: mov byte ptr [di],DRIVEEXIST
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jmp nextsetfloppy
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chkfloppy: dec bh ; dec actual drive count
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js nextsetfloppy
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mov byte ptr [di+1],REMOVEDRV
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mov byte ptr [di+3],FLOPPY
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jmp setfloppyexist
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nextsetfloppy: add di,4
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inc bl
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cmp bl,2 ; if B then jump back
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je nextchkfloppy
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mov ch,24 ; loop 24 times (drives C - Z)
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mov cl,3 ; start at C:
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drivechkloop: mov ax,4409h ; check if drive exists
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mov bl,cl ; set drive letter
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int 21h ; 0 = default, 1 = A:, etc.
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jc nextsetdrv
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mov byte ptr [di],DRIVEEXIST
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mov ax,4408h ; check if removable
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int 21h
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mov byte ptr [di+1],al ; set REMOVABLE or FIXED
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mov bx,dx
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mov dl,dh
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shr dl,7
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and dh,00010000b
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shr dh,4
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mov byte ptr [di+2],dh ; set REMOTE or LOCAL
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or dl,dl ; if not SUBST, then jump
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jz chkremote
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mov byte ptr [di+3],SUBST
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jmp nextsetdrv
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chkremote: cmp dh,REMOTEDRV ; if REMOTE, then check for CD ROM
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je chkcdrom
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test bh,00000010b ; sharable?
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jz drivenoshare
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mov byte ptr [di+2],SHAREDRV
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drivenoshare: test bl,00000010b ; RAM drive?
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jnz nextsetdrv
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mov byte ptr [di+3],RAM
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jmp nextsetdrv
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chkcdrom: push cx
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mov ax,1500h
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xor bx,bx
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int 2fh
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pop cx
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or bx,bx ; MSCDEX driver found?
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jz nextsetdrv ; if not, jump to next drive setup
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mov ax,150bh
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dec cl ; 0=A:, etc.
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int 2fh
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inc cl
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or ax,ax
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jz nextsetdrv ; drive supported by MSCDEX?
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mov byte ptr [di+3],CDROM
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nextsetdrv: add di,4
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inc cl
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dec ch
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jnz drivechkloop
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pop dx
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mov ah,0eh
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int 21h ; reset start drive
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pop es
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popa
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ret
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_Drives_Exist ENDP
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END
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